I read a couple of articles and looked at the map. There is a road right up to the lake and apparently some buildings nearby. One article said that they never found his truck either.

So, it seems likely he either never made it to the lake or made it and also left. Maybe there is a slight possibility that he did get lost near the lake and his truck was subsequently stolen.

I'm thinking the most likely scenario is that he drove off the road somewhere along the way.